GENERAL PRECAUTIONS
Extreme care must be exercised with respect to the administration of additional sympathomimetic agents.
Since metaproterenol is a sympathomimetic amine, it should be used with caution in patients with cardiovascular disorders, including ischemic heart disease, hypertension or cardiac arrhythmias, in patients with hyperthyroidism or diabetes mellitus, and in patients who are unusually responsive to sympathomimetic amines or who have convulsive disorders. Significant changes in systolic and diastolic blood pressure could be expected to occur in some patients after use of any beta adrenergic bronchodilator.
Information for Patients
Appropriate care should be exercised when considering the administration of additional sympathomimetic agents. A sufficient interval of time should elapse prior to administration of another sympathomimetic agent. Metaproterenol should not be used more often than prescribed. If symptoms persist, patients should consult a physician promptly.
Drug Interactions
Beta adrenergic agonists should be administered with caution to patients being treated with monoamine oxidase inhibitors or tricyclic antidepressants, since the action of beta adrenergic agonists on the vascular system may be potentiated.
Carcinogenesis and Mutagenesis and Impairment of Fertility
In an 18-month study in mice, metaproterenol produced a significant increase in benign hepatic adenomas in males and benign ovarian tumors in females at doses corresponding to 31 and 62 times the maximum recommended dose (based on a 50 kg individual). In a two-year study in rats, a non-significant incidence of benign leiomyomata of the mesovarium was noted at 62 times the maximum recommended dose. The relevance of these findings to man is not known. Mutagenicity studies with metaproterenol have not been conducted. Reproduction studies in rats revealed no evidence of impaired fertility.
Pregnancy
Teratogenic Effects: Pregnancy Category C: Metaproterenol sulfate has been shown to be teratogenic and embryotoxic in rabbits when given orally at doses of 100 mg/kg or 62 times the maximum recommended human oral dose. These effects included skeletal abnormalities, hydrocephalus and skull bone separation. Embryotoxicity has also been shown in mice when given orally at doses of 50 mg/kg or 31 times the maximum recommended human oral dose. Results of other oral reproduction studies in rats (40 mg/kg) and rabbits (50 mg/kg) have not revealed any teratogenic, embryotoxic or fetotoxic effects. There are no adequate and well-controlled studies in pregnant women. Metaproterenol sulfate should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Nursing Mothers
It is not known whether metaproterenol is excreted in human milk; therefore, metaproterenol should be used during nursing only if the potential benefit justifies the possible risk to the newborn.
Pediatric Use
Metaproterenol sulfate tablets are not recommended for use in children under six years of age because of insufficient clinical data to establish safety and effectiveness.
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